The main component of the tooth is hydroxyapatite. In the oral cavity, elution of phosphate ions and calcium ions (decalcification) and crystallization into calcium phosphate and hydroxyapatite (remineralization) are normally in equilibrium. Bacteria such as Streptococcus mutans decompose sucrose and the like to produce organic acids and lower pH. Because of that, calcium and the like of the teeth are eluted to promote decalcification, which leads to the progression of dental caries. In the initial stage of dental caries, the decalcified lesion beneath the surface of the tooth called as a white spot is formed in enamel. It is known that, at that stage, fluoride ions promote crystallization of calcium ions and phosphate ions, i.e., remineralization, to thereby enable prevention of dental caries and elimination of such white spot.
On the other hand, sugar alcohols such as xylitol are known to be nonfermentable and to have an action of suppressing growth of cariogenic bacteria. Patent Document 1 has reported a composition for oral cavity containing xylitol and a fluorine compound in a certain ratio. In addition, as a technique to promote remineralization by a fluorine compound, Patent Document 2 describes a composition for oral cavity containing a sugar alcohol such as xylitol, sodium fluoride and magnesium ions, and Patent Document 3 describes a composition for oral cavity containing Palatinit and a fluorine compound and shows the results that as the content of Palatinit increases, the amount of remineralization becomes large.